The Fire Service called lifeguards to help with the response about 12.30pm.
An Inflatable Rescue Boat (IRB) was already patrolling the water at Whangamata and headed to Donut Island, Surf Life Saving NZ spokeswoman Lisa Smith said. A second IRB also responded.
Lifeguards helped give the man CPR. They brought him back to the beach where more lifeguards were waiting with a defibrillator and emergency services were standing by, Smith said.
Surfsup offered guided tours to the island, and hired equipment for those who wanted to make their way independently, said guide Chris Murnane.
When he saw the man being brought to the beach he checked to see if he was a client, but the man did not appear to be using hired gear.
He then backed away, Murnane said.
"The tarp went up and they were doing their [resuscitation]."
Conditions were perfect for kayaking to the island today, with four to six knot winds and an 0.4 metre swell, he said.
According to the town's tourism website, the island is one kilometre offshore.
"A well-kept local secret, Donut Island has two small beaches in the centre of the island's collapsed blowhole."